Spiral Upgrade: Six Months In Review

Six months after its activation on February 5, 2024, the Spiral network upgrade has proven stable and successful — bringing Ethereum Classic's EVM to parity with Ethereum's Shanghai execution-layer improvements.

## What Spiral Delivered

Spiral (ECIP-1109) implemented seven EIPs from Ethereum's Shanghai upgrade:

- **EIP-3651 — Warm COINBASE**: Reduced gas cost for accessing the block producer's address from 2,600 to 100 gas. Benefits MEV and staking-related contracts.
- **EIP-3855 — PUSH0**: New opcode that pushes zero onto the stack at minimal cost. Reduces bytecode size across all new deployments.
- **EIP-3860 — Limit and Meter initcode**: Caps initcode size at 49,152 bytes and charges 2 gas per 32-byte word. Prevents oversized deployment transactions.
- **EIP-4200 — Static Relative Jumps**: Introduces RJUMP, RJUMPI, and RJUMPV opcodes for more efficient control flow in EVM bytecode.
- **EIP-6049 — Deprecate SELFDESTRUCT**: Formal deprecation notice for the SELFDESTRUCT opcode.

## Omitted EIPs

As with previous upgrades, ETC excluded PoS-specific changes:

- **EIP-4399 (PREVRANDAO)**: Replaces DIFFICULTY with beacon chain randomness — only applicable to proof-of-stake
- **EIP-4895 (Beacon Chain Withdrawals)**: Validator withdrawals — only applicable to proof-of-stake

## Network Impact

### Stability
Zero chain splits, zero client incompatibilities. All three ETC clients (Core-Geth, Besu, Fukuii) processed the fork boundary without issues.

### Developer Experience
EVM parity with Shanghai means developers can use the latest Solidity compiler features when deploying to ETC. Tools like Hardhat, Foundry, and Remix work without special configuration.

### Gas Efficiency
PUSH0 and Warm COINBASE have measurably reduced gas costs for common operations, benefiting all users.

## Current Status

Spiral represents ETC's current production EVM level. The next planned upgrade, Olympia, will introduce the treasury funding mechanism via EIP-1559 base fee redirection.